A known printer includes a sheet cassette that includes a sheet support plate configured to movably support a stack of one or more sheets in an up-down direction, and a raising gear configured to raise the sheet support plate. The printer further includes a driving gear configured to be driven by a motor. With the sheet cassette mounted in or attached to a casing of the printer, the driving gear and the raising gear are coupled to or engaged with each other to allow drive force from the motor to be supplied to the sheet support plate. The sheet support plate is raised by the drive force to a sheet feedable position where a sheet on the sheet support plate is allowed to be fed.
The printer estimates an amount of sheets stacked on the sheet support plate by measuring a period of time for the sheet support plate to reach the sheet feedable position from the lowest position.
With the sheet cassette attached to the casing, the driving gear is engaged with the raising gear, which enables the sheet support plate to be held in a raised position even if the motor is stopped. With the sheet cassette separated from the casing, the driving gear and the raising gear are disengaged from each other, which allows the sheet support plate to be lowered by its own weight to the lowest positon.
Engaging the raising gear with the driving gear may cause rotation of the raising gear relative to the driving gear. This rotation may cause the sheet support plate at the lowest position to be raised.